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Subject: RE: [PATCH] RE: [cfe-dev] missing return statement for non-void functions in C++
From: "Sjoerd Meijer" <sjoerd.meijer () arm ! com>
Date: 2015-08-03 10:40:14
Message-ID: 001101d0cdd8$c80a4290$581ec7b0$ () arm ! com
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Hi Richard,
I agree with your conclusions and will start preparing a patch for option 3) under a \
flag that is off by default; this enables folks to build/run C code in C++. I \
actually think option 2) would be a good one too, but as it is already available \
under a flag I also don't see how useful it is combining options 2) and 3) with \
another (or one more) flag that is off by default.
Cheers.
From: metafoo@gmail.com [mailto:metafoo@gmail.com] On Behalf Of Richard Smith
Sent: 31 July 2015 19:46
To: Sjoerd Meijer
Cc: Hal Finkel; Marshall Clow; cfe-dev@cs.uiuc.edu Developers; cfe commits
Subject: Re: [PATCH] RE: [cfe-dev] missing return statement for non-void functions in \
C++
On Fri, Jul 31, 2015 at 7:35 AM, Sjoerd Meijer <sjoerd.meijer@arm.com> wrote:
Hi, I am not sure if we came to a conclusion. Please find attached a patch. It simply \
removes the two lines that insert an unreachable statement (which cause removal of \
the return statement). Please note that at -O0 the trap instruction is still \
generated. Is this something we could live with?
I don't think this is an improvement:
This doesn't satisfy the folks who want an 'unreachable' for better code size and \
optimization, and it doesn't satisfy the folks who want a guaranteed trap for \
security, and it doesn't satisfy the folks who want their broken code to limp along \
(because it'll still trap at -O0), and it is at best a minor improvement for the \
folks who want missing returns to be more easily debuggable (with -On, the code goes \
wrong in the caller, or appears to work, rather than falling into an unrelated \
function, and debugging this with -O0 was already easy).
I think there are three options that are defensible here:
1) The status quo: this is UB and we treat it as such and optimize on that basis, but \
provide a trap as a convenience at -O0
2) The secure approach: this is UB but we always trap
3) Define the behavior to return 'undef' for C types: this allows questionable C code \
that has UB in C++ to keep working when built with a C++ compiler
Note that (3) can be combined with either (1) or (2). (2) is already available via \
the 'return' sanitizer. So this really reduces to: in those cases where C says it's \
OK so long as the caller doesn't look at the returned value (and where the return \
type doesn't have a non-trivial copy constructor or destructor, isn't a reference, \
and so on), should we attempt to preserve the C behaviour? I would be OK with putting \
that behind a `-f` flag (perhaps `-fstrict-return` or similar) to support those folks \
who want to build C code in C++, but I would suggest having that flag be off by \
default, since that is not the usual use case for a C++ compiler.
Cheers,
Sjoerd.
From: cfe-dev-bounces@cs.uiuc.edu [mailto:cfe-dev-bounces@cs.uiuc.edu] On Behalf Of \
Richard Smith
Sent: 29 July 2015 18:07
To: Hal Finkel
Cc: Marshall Clow; cfe-dev@cs.uiuc.edu Developers
Subject: Re: [cfe-dev] missing return statement for non-void functions in C++
On Jul 29, 2015 7:43 AM, "Hal Finkel" <hfinkel@anl.gov> wrote:
>
> ----- Original Message -----
> > From: "David Blaikie" <dblaikie@gmail.com>
> > To: "James Molloy" <james@jamesmolloy.co.uk>
> > Cc: "Marshall Clow" <mclow.lists@gmail.com>, "cfe-dev Developers" \
> > <cfe-dev@cs.uiuc.edu>
> > Sent: Wednesday, July 29, 2015 9:15:09 AM
> > Subject: Re: [cfe-dev] missing return statement for non-void functions in C++
> >
> >
> > On Jul 29, 2015 7:06 AM, "James Molloy" < james@jamesmolloy.co.uk >
> > wrote:
> > >
> > > Hi,
> > >
> > > If we're going to emit a trap instruction (and thus create a broken
> > > binary), why don't we error instead?
> >
> > We warn, can't error, because it may be dynamically unreached, in
> > which case the program is valid and we can't reject it.
>
> I think this also explains why this is useful for optimization.
>
> 1. It is a code-size optimization
> 2. By eliminating unreachable control flow, we can remove branches and tests that \
> are not actual necessary
> int foo(int x) {
> if (x > 5) return 2*x;
> else if (x < 2) return 3 - x;
> }
>
> That having been said, there are other ways to express these things, and the \
> situation often represents an error. I'd be fine with requiring a special flag \
> (-fallow-nonreturning-functions or whatever) in order to put the compiler is a \
> truly confirming mode (similar to the situation with sized delete).
Note that we already have a flag to trap on this: -fsanitize-trap=return. (You may \
also need -fsanitize=return, I don't remember.) That seems consistent with how we \
treat most other forms of UB.
> -Hal
>
> >
> > >
> > > James
> > >
> > > On Wed, 29 Jul 2015 at 15:05 David Blaikie < dblaikie@gmail.com >
> > > wrote:
> > > >
> > > >
> > > > On Jul 29, 2015 2:10 AM, "mats petersson" < mats@planetcatfish.com
> > > > > wrote:
> > > > >
> > > > >
> > > > >
> > > > > On 28 July 2015 at 23:40, Marshall Clow < mclow.lists@gmail.com
> > > > > > wrote:
> > > > > >
> > > > > >
> > > > > >
> > > > > > On Tue, Jul 28, 2015 at 6:14 AM, Sjoerd Meijer <
> > > > > > sjoerd.meijer@arm.com > wrote:
> > > > > > >
> > > > > > > Hi,
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > In C++, the undefined behaviour of a missing return statements
> > > > > > > for a non-void function results in not generating the
> > > > > > > function epilogue (unreachable statement is inserted and the
> > > > > > > return statement is optimised away). Consequently, the
> > > > > > > runtime behaviour is that control is never properly returned
> > > > > > > from this function and thus it starts executing "garbage
> > > > > > > instructions". As this is undefined behaviour, this is
> > > > > > > perfectly fine and according to the spec, and a compile
> > > > > > > warning for this missing return statement is issued. However,
> > > > > > > in C, the behaviour is that a function epilogue is generated,
> > > > > > > i.e. basically by returning uninitialised local variable.
> > > > > > > Codes that rely on this are not beautiful pieces of code, i.e
> > > > > > > are buggy, but it might just be okay if you for example have
> > > > > > > a function that just initialises stuff (and the return value
> > > > > > > is not checked, directly or indirectly); some one might argue
> > > > > > > that not returning from that function might be a bit harsh.
> > > > > >
> > > > > >
> > > > > > I would not be one of those people.
> > > > >
> > > > >
> > > > > Nor me.
> > > > > >
> > > > > >
> > > > > > >
> > > > > > > So this email is to probe if there would be strong resistance
> > > > > > > to follow the C behaviour? I am not yet sure how, but would
> > > > > > > perhaps a compromise be possible/acceptable to make the
> > > > > > > undefined behaviour explicit and also generate the function
> > > > > > > epilogue?
> > > > > >
> > > > > >
> > > > > > "undefined behavior" is exactly that.
> > > > > >
> > > > > > You have no idea what is going to happen; there are no
> > > > > > restrictions on what the code being executed can do.
> > > > > >
> > > > > > "it just might be ok" means on a particular version of a
> > > > > > particular compiler, on a particular architecture and OS, at a
> > > > > > particular optimization level. Change any of those things, and
> > > > > > you can change the behavior.
> > > > >
> > > > >
> > > > > In fact, the "it works kind of as you expected" is the worst
> > > > > kind of UB in my mind. UB that causes a crash, stops or other
> > > > > "directly obvious that this is wrong" are MUCH easier to debug.
> > > > >
> > > > > So make this particular kind of UB explicit by crashing or
> > > > > stopping would be a good thing. Making it explicit by
> > > > > "returning kind of nicely, but not correct return value" is
> > > > > about the worst possible result.
> > > >
> > > > At -O0 clang emits a trap instruction, making it more explicit as
> > > > you suggest. At higher optimization levels it just falls
> > > > through/off.
> > > >
> > > > >
> > > > > --
> > > > > Mats
> > > > > >
> > > > > >
> > > > > > -- Marshall
> > > > > >
> > > > > >
> > > > > > _______________________________________________
> > > > > > cfe-dev mailing list
> > > > > > cfe-dev@cs.uiuc.edu
> > > > > > http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
> > > > > >
> > > > >
> > > > >
> > > > > _______________________________________________
> > > > > cfe-dev mailing list
> > > > > cfe-dev@cs.uiuc.edu
> > > > > http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
> > > > >
> > > >
> > > > _______________________________________________
> > > > cfe-dev mailing list
> > > > cfe-dev@cs.uiuc.edu
> > > > http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
> >
> > _______________________________________________
> > cfe-dev mailing list
> > cfe-dev@cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
> >
>
> --
> Hal Finkel
> Assistant Computational Scientist
> Leadership Computing Facility
> Argonne National Laboratory
>
> _______________________________________________
> cfe-dev mailing list
> cfe-dev@cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
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class=WordSection1><p class=MsoNormal><span \
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Hi \
Richard,<o:p></o:p></span></p><p class=MsoNormal><span \
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p \
class=MsoNormal><span \
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>I agree \
with your conclusions and will start preparing a patch for option 3) under a flag \
that is off by default; this enables folks to build/run C code in C++. I actually \
think option 2) would be a good one too, but as it is already available under a flag \
I also don't see how useful it is combining options 2) and 3) with another (or one \
more) flag that is off by default.<o:p></o:p></span></p><p class=MsoNormal><span \
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p \
class=MsoNormal><span \
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Cheers.<o:p></o:p></span></p><p \
class=MsoNormal><span \
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p \
class=MsoNormal><b><span lang=EN-US \
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span \
lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> \
metafoo@gmail.com [mailto:metafoo@gmail.com] <b>On Behalf Of </b>Richard \
Smith<br><b>Sent:</b> 31 July 2015 19:46<br><b>To:</b> Sjoerd Meijer<br><b>Cc:</b> \
Hal Finkel; Marshall Clow; cfe-dev@cs.uiuc.edu Developers; cfe \
commits<br><b>Subject:</b> Re: [PATCH] RE: [cfe-dev] missing return statement for \
non-void functions in C++<o:p></o:p></span></p><p \
class=MsoNormal><o:p> </o:p></p><div><div><div><p class=MsoNormal>On Fri, Jul \
31, 2015 at 7:35 AM, Sjoerd Meijer <<a href="mailto:sjoerd.meijer@arm.com" \
target="_blank">sjoerd.meijer@arm.com</a>> wrote:<o:p></o:p></p><div><p \
class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span \
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Hi, I am \
not sure if we came to a conclusion. Please find attached a patch. It simply removes \
the two lines that insert an unreachable statement (which cause removal of the return \
statement). Please note that at -O0 the trap instruction is still generated. Is this \
something we could live with?</span><o:p></o:p></p></div><div><p \
class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>I don't think this \
is an improvement:<o:p></o:p></p></div><div><p \
class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>This doesn't \
satisfy the folks who want an 'unreachable' for better code size and optimization, \
and it doesn't satisfy the folks who want a guaranteed trap for security, and it \
doesn't satisfy the folks who want their broken code to limp along (because it'll \
still trap at -O0), and it is at best a minor improvement for the folks who want \
missing returns to be more easily debuggable (with -On, the code goes wrong in the \
caller, or appears to work, rather than falling into an unrelated function, and \
debugging this with -O0 was already easy).<o:p></o:p></p></div><div><p \
class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>I think there are \
three options that are defensible here:<o:p></o:p></p></div><div><p \
class=MsoNormal>1) The status quo: this is UB and we treat it as such and optimize on \
that basis, but provide a trap as a convenience at -O0<o:p></o:p></p></div><div><p \
class=MsoNormal>2) The secure approach: this is UB but we always \
trap<o:p></o:p></p></div><div><p class=MsoNormal>3) Define the behavior to return \
'undef' for C types: this allows questionable C code that has UB in C++ to keep \
working when built with a C++ compiler<o:p></o:p></p></div><div><p \
class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Note that (3) can \
be combined with either (1) or (2). (2) is already available via the 'return' \
sanitizer. So this really reduces to: in those cases where C says it's OK so long as \
the caller doesn't look at the returned value (and where the return type doesn't have \
a non-trivial copy constructor or destructor, isn't a reference, and so on), should \
we attempt to preserve the C behaviour? I would be OK with putting that behind a `-f` \
flag (perhaps `-fstrict-return` or similar) to support those folks who want to build \
C code in C++, but I would suggest having that flag be off by default, since that is \
not the usual use case for a C++ compiler.<o:p></o:p></p></div><div><p \
class=MsoNormal><o:p> </o:p></p></div><blockquote \
style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0cm 0cm 0cm \
6.0pt;margin-left:4.8pt;margin-right:0cm'><div><p class=MsoNormal \
style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span \
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Cheers,</span><o:p></o:p></p><p \
class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span \
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Sjoerd.</span><o:p></o:p></p><p \
class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span \
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'> </span><o:p></o:p></p><p \
class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><b><span \
lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span \
lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> <a \
href="mailto:cfe-dev-bounces@cs.uiuc.edu" \
target="_blank">cfe-dev-bounces@cs.uiuc.edu</a> [mailto:<a \
href="mailto:cfe-dev-bounces@cs.uiuc.edu" \
target="_blank">cfe-dev-bounces@cs.uiuc.edu</a>] <b>On Behalf Of </b>Richard \
Smith<br><b>Sent:</b> 29 July 2015 18:07<br><b>To:</b> Hal Finkel<br><b>Cc:</b> \
Marshall Clow; <a href="mailto:cfe-dev@cs.uiuc.edu" \
target="_blank">cfe-dev@cs.uiuc.edu</a> Developers</span><o:p></o:p></p><div><div><p \
class=MsoNormal><br><b>Subject:</b> Re: [cfe-dev] missing return statement for \
non-void functions in C++<o:p></o:p></p></div></div><div><div><p class=MsoNormal \
style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><p>On \
Jul 29, 2015 7:43 AM, "Hal Finkel" <<a href="mailto:hfinkel@anl.gov" \
target="_blank">hfinkel@anl.gov</a>> wrote:<br>><br>> ----- Original Message \
-----<br>> > From: "David Blaikie" <<a \
href="mailto:dblaikie@gmail.com" target="_blank">dblaikie@gmail.com</a>><br>> \
> To: "James Molloy" <<a href="mailto:james@jamesmolloy.co.uk" \
target="_blank">james@jamesmolloy.co.uk</a>><br>> > Cc: "Marshall \
Clow" <<a href="mailto:mclow.lists@gmail.com" \
target="_blank">mclow.lists@gmail.com</a>>, "cfe-dev Developers" <<a \
href="mailto:cfe-dev@cs.uiuc.edu" target="_blank">cfe-dev@cs.uiuc.edu</a>><br>> \
> Sent: Wednesday, July 29, 2015 9:15:09 AM<br>> > Subject: Re: [cfe-dev] \
missing return statement for non-void functions in C++<br>> ><br>> \
><br>> > On Jul 29, 2015 7:06 AM, "James Molloy" < <a \
href="mailto:james@jamesmolloy.co.uk" target="_blank">james@jamesmolloy.co.uk</a> \
><br>> > wrote:<br>> > ><br>> > > Hi,<br>> > \
><br>> > > If we're going to emit a trap instruction (and thus create a \
broken<br>> > > binary), why don't we error instead?<br>> ><br>> \
> We warn, can't error, because it may be dynamically unreached, in<br>> > \
which case the program is valid and we can't reject it.<br>><br>> I think this \
also explains why this is useful for optimization.<br>><br>> 1. It is a \
code-size optimization<br>> 2. By eliminating unreachable control flow, we \
can remove branches and tests that are not actual necessary<br>><br>> int \
foo(int x) {<br>> if (x > 5) return 2*x;<br>> else if (x < \
2) return 3 - x;<br>> }<br>><br>> That having been said, there are other \
ways to express these things, and the situation often represents an error. I'd be \
fine with requiring a special flag (-fallow-nonreturning-functions or whatever) in \
order to put the compiler is a truly confirming mode (similar to the situation with \
sized delete).<o:p></o:p></p><p>Note that we already have a flag to trap on this: \
-fsanitize-trap=return. (You may also need -fsanitize=return, I don't remember.) That \
seems consistent with how we treat most other forms of UB.<o:p></o:p></p><p>> \
-Hal<br>><br>> ><br>> > ><br>> > > James<br>> \
> ><br>> > > On Wed, 29 Jul 2015 at 15:05 David Blaikie < <a \
href="mailto:dblaikie@gmail.com" target="_blank">dblaikie@gmail.com</a> ><br>> \
> > wrote:<br>> > >><br>> > >><br>> > >> On \
Jul 29, 2015 2:10 AM, "mats petersson" < <a \
href="mailto:mats@planetcatfish.com" \
target="_blank">mats@planetcatfish.com</a><br>> > >> > wrote:<br>> \
> >> ><br>> > >> ><br>> > >> ><br>> > \
>> > On 28 July 2015 at 23:40, Marshall Clow < <a \
href="mailto:mclow.lists@gmail.com" target="_blank">mclow.lists@gmail.com</a><br>> \
> >> > > wrote:<br>> > >> >><br>> > >> \
>><br>> > >> >><br>> > >> >> On Tue, Jul \
28, 2015 at 6:14 AM, Sjoerd Meijer <<br>> > >> >> <a \
href="mailto:sjoerd.meijer@arm.com" target="_blank">sjoerd.meijer@arm.com</a> > \
wrote:<br>> > >> >>><br>> > >> >>> \
Hi,<br>> > >> >>><br>> > >> >>><br>> \
> >> >>><br>> > >> >>> In C++, the undefined \
behaviour of a missing return statements<br>> > >> >>> for a \
non-void function results in not generating the<br>> > >> >>> \
function epilogue (unreachable statement is inserted and the<br>> > >> \
>>> return statement is optimised away). Consequently, the<br>> > \
>> >>> runtime behaviour is that control is never properly \
returned<br>> > >> >>> from this function and thus it starts \
executing "garbage<br>> > >> >>> instructions". As this is \
undefined behaviour, this is<br>> > >> >>> perfectly fine and \
according to the spec, and a compile<br>> > >> >>> warning for \
this missing return statement is issued. However,<br>> > >> >>> \
in C, the behaviour is that a function epilogue is generated,<br>> > >> \
>>> i.e. basically by returning uninitialised local variable.<br>> > \
>> >>> Codes that rely on this are not beautiful pieces of code, \
i.e<br>> > >> >>> are buggy, but it might just be okay if you \
for example have<br>> > >> >>> a function that just initialises \
stuff (and the return value<br>> > >> >>> is not checked, \
directly or indirectly); some one might argue<br>> > >> >>> that \
not returning from that function might be a bit harsh.<br>> > >> \
>><br>> > >> >><br>> > >> >> I would not be \
one of those people.<br>> > >> ><br>> > >> ><br>> \
> >> > Nor me.<br>> > >> >><br>> > >> \
>><br>> > >> >>><br>> > >> >>> So \
this email is to probe if there would be strong resistance<br>> > >> \
>>> to follow the C behaviour? I am not yet sure how, but would<br>> > \
>> >>> perhaps a compromise be possible/acceptable to make the<br>> \
> >> >>> undefined behaviour explicit and also generate the \
function<br>> > >> >>> epilogue?<br>> > >> \
>><br>> > >> >><br>> > >> >> \
"undefined behavior" is exactly that.<br>> > >> \
>><br>> > >> >> You have no idea what is going to happen; \
there are no<br>> > >> >> restrictions on what the code being \
executed can do.<br>> > >> >><br>> > >> >> \
"it just might be ok" means on a particular version of a<br>> > \
>> >> particular compiler, on a particular architecture and OS, at \
a<br>> > >> >> particular optimization level. Change any of those \
things, and<br>> > >> >> you can change the behavior.<br>> > \
>> ><br>> > >> ><br>> > >> > In fact, the \
"it works kind of as you expected" is the worst<br>> > >> > \
kind of UB in my mind. UB that causes a crash, stops or other<br>> > >> \
> "directly obvious that this is wrong" are MUCH easier to \
debug.<br>> > >> ><br>> > >> > So make this particular \
kind of UB explicit by crashing or<br>> > >> > stopping would be a \
good thing. Making it explicit by<br>> > >> > "returning kind of \
nicely, but not correct return value" is<br>> > >> > about the \
worst possible result.<br>> > >><br>> > >> At -O0 clang emits \
a trap instruction, making it more explicit as<br>> > >> you suggest. At \
higher optimization levels it just falls<br>> > >> through/off.<br>> \
> >><br>> > >> ><br>> > >> > --<br>> > \
>> > Mats<br>> > >> >><br>> > >> \
>><br>> > >> >> -- Marshall<br>> > >> \
>><br>> > >> >><br>> > >> >> \
_______________________________________________<br>> > >> >> \
cfe-dev mailing list<br>> > >> >> <a \
href="mailto:cfe-dev@cs.uiuc.edu" target="_blank">cfe-dev@cs.uiuc.edu</a><br>> \
> >> >> <a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev" \
target="_blank">http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev</a><br>> > \
>> >><br>> > >> ><br>> > >> ><br>> > \
>> > _______________________________________________<br>> > >> \
> cfe-dev mailing list<br>> > >> > <a \
href="mailto:cfe-dev@cs.uiuc.edu" target="_blank">cfe-dev@cs.uiuc.edu</a><br>> \
> >> > <a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev" \
target="_blank">http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev</a><br>> > \
>> ><br>> > >><br>> > >> \
_______________________________________________<br>> > >> cfe-dev mailing \
list<br>> > >> <a href="mailto:cfe-dev@cs.uiuc.edu" \
target="_blank">cfe-dev@cs.uiuc.edu</a><br>> > >> <a \
href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev" \
target="_blank">http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev</a><br>> \
><br>> > _______________________________________________<br>> > \
cfe-dev mailing list<br>> > <a href="mailto:cfe-dev@cs.uiuc.edu" \
target="_blank">cfe-dev@cs.uiuc.edu</a><br>> > <a \
href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev" \
target="_blank">http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev</a><br>> \
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